With the development of the industry, soil becomes contaminated with hazardous substances like oil and heavy metals, and so as to remediate the contaminated soil, thus, compositions or devices for washing the contaminated soil have been suggested.
One example of such soil washing devices is disclosed in Korean Patent Laid-Open Application No. 2003-0005713 (dated on Jan. 23, 2003) wherein the soil washing device includes a pre-washing tank and a main washing tank by which the contaminated soil can be repeatedly washed.
Further, the conventional soil washing device is configured wherein the contaminated soil is collected and poured into a mixing tank for remediation.
In this case, referring to FIG. 1 showing general soil remediation efficiencies in accordance with the particle sizes of soil, soil is separated into coarse soil such as gravel and stone having particle sizes of more than 2 mm, medium soil such as sand having particle sizes between 0.075 mm and 2 mm, and fine soil such as silt and clay having particle sizes of less than 0.075 mm. If the coarse soil, the medium soil and the fine soil are remediated, in view of the remediation cost and time efficiency, the coarse soil is within a substantially economical range, the fine soil is within inefficient economical range, and the medium soil is within intermediate economical range.
However, disadvantageously, the conventional soil washing devices just perform the remediation of all of the contaminated soil, irrespective of soil properties and the soil contamination degrees caused by the soil properties, that is, irrespective of the differences of the particle sizes of soil on a paddy field, farm, seaside and mountain range and the contamination degrees of the soil by particle size, thereby showing low efficiencies in remediation work.